Abstract: For the design of man-machine operation interaction in the complexity and speed man-machine system the results showed, that using different response modality (foot-hand) did not eliminate and reduce PRP interference, and could not raise the performance of overlapped -task. But lowering the complexity of selecting response could raise the performance of overlapped -task. The grade of complexity of selecting respose was in direct proportion to the degree of PRP (psychological refractory period) interfe rence.

Key words: psychological refractory period, overlapping-task, man-machine operation interaction, response similarily effects